The present invention is directed to a compound bow that is capable of 100% let-off, a cam which permits 100% let-off, and an adjustable deflector to adjust the actual let-off to an archer-determined level.
Compound bows are used in both competitive archery and hunting small and large game. Modern day bows can require significant amounts of force to retract the nocked arrow to full draw. It then becomes problematic to retain the arrow in the firing position since holding against 50–100 pounds of force for any length of time will produce muscle fatigue which can influence the accuracy of the shot. In order to reduce the strain, some archers will pull the bow to less draw weight which negatively affects arrow speed that in turn reduces distance, target penetration and arrow trajectory.
In order to cope with this problem, some of today's compound bow systems have taken one of two approaches: 1) employment of a locking system that will hold the nocked arrow at full draw; or, 2) using a cam system which permits a reduction in the holding force, commonly known as let-off. The current systems have gradually moved the achievable let-off from 50% to as high, in some cases, as 85%. Even holding 15% of the draw force of a 100 pound bow (15 pounds) for extended periods of time in order to access a target, can produce muscle strain leading to an inaccurate shot.
It is an object of the present invention to provide a compound bow that is capable of 100% let-off. Hence, the bow may be adjusted to permit the bow to be held at full draw with as little as 0.001% of the draw force (0.1 pound for a 100 pound bow). With the present design, the archer can adjust the let-off to whatever level of let-off he or she desires in the range of between 85% and just under 100%. This means that the archer can hold the bow at full draw for extended periods of time without producing muscle fatigue that will negatively impact the shot. Accordingly, the nocked arrow can be drawn to firing position prior to the animal entering the shooting zone, reducing the risk of detection resulting from movement and/or sound.
The compound bow of the present invention comprises a riser; a limb connected to the riser; an eccentric cam mounted on the limb; a harness cable wrapped about at least a portion of said eccentric cam, the cable having a force line and requiring a particular level of draw force and retaining force; an axle pin mounting the cam to the limb and about which the cam rotates; means to permit the force line of the cable to effectively act through the axle pin enabling said cam to effect 100% let-off of said retaining force; means to adjust said retaining force to a user desired level less than 100% let-off. The means for permitting the force line of the cable to effectively act through the axle pin can include a notched axle pin, a two-piece axle pin, a deflector which adjusts the path of the cable to extend around the axle pin. With a single cam compound bow, an eccentric bushing may be employed to deflect the harness cable in a direction outwardly from the axle pin to produce an archer-selected level of let-off in the range of between 85% and 99+%. With a double cam bow, the level of let-off may be altered by replacing a modular tip of the cam to alter the amount of deflection of the harness cable and, hence, the amount of let-off.
It will be understood that a variety of different pivot means can be utilized with the cams of the present invention. While the term “pivot axle” has been utilized herein, it is intended that any and all such pivot means as may be substituted for the pivot pin shown herein be included in the scope of the present invention.
Various other features, advantages and characteristics of the present invention will become apparent to one of ordinary skill in the art after a reading of the following specification.